Studies included assessed the impact of human-made, intentional, terrorist attacks in direct victims and/or persons in general population and evaluated MDD based on diagnostic criteria..
Trang 1R E S E A R C H A R T I C L E Open Access
Major depressive disorder following terrorist
attacks: A systematic review of prevalence, course and correlates
José M Salguero1*, Pablo Fernández-Berrocal2, Itziar Iruarrizaga3, Antonio Cano-Vindel3and Sandro Galea4
Abstract
Background: Terrorist attacks are traumatic events that may result in a wide range of psychological disorders for people exposed This review aimed to systematically assess the current evidence on major depressive disorder (MDD) after terrorist attacks
Methods: A systematic review was performed Studies included assessed the impact of human-made, intentional, terrorist attacks in direct victims and/or persons in general population and evaluated MDD based on diagnostic criteria
Results: A total of 567 reports were identified, 11 of which were eligible for this review: 6 carried out with direct victims, 4 with persons in general population, and 1 with victims and general population The reviewed literature suggests that the risk of MDD ranges between 20 and 30% in direct victims and between 4 and 10% in the
general population in the first few months after terrorist attacks Characteristics that tend to increase risk of MDD after a terrorist attack are female gender, having experienced more stressful situations before or after the attack, peritraumatic reactions during the attack, loss of psychosocial resources, and low social support The course of MDD after terrorist attacks is less clear due to the scarcity of longitudinal studies
Conclusions: Methodological limitations in the literature of this field are considered and potentially important areas for future research such as the assessment of the course of MDD, the study of correlates of MDD or the comorbidity between MDD and other mental health problems are discussed
Background
The scientific study of the psychological consequences
of disasters has come a long way in the last decade
[1,2] Different reviews of the topic have shown that
dis-asters are a relatively common event in western
coun-tries [3] capable of affecting the population in which
they occur as a whole [4]
Of the different types of disasters, terrorism occupies a
special place in the literature Terrorism is defined as
‘’the intentional use of violence against one or more
non-combatants and/or those services essential for or
protective of their health, resulting in adverse health
effects in those immediately affected and their
community, ranging from a loss of well-being or secur-ity to injury, illness, or death’’ [5] The results of several revisions of the consequences of disasters have shown that terrorism may be associated with a greater risk of psychopathology than other disasters [6] This character-istic, along with the increase in terrorist attacks that have struck various cities of the USA and Europe in recent years, have turned terrorism into a problem of interest, both for clinicians and for public health professionals
A substantial body of research, much of which has been carried out after the September 11, 2001 terrorist attacks in New York and the March 11, 2004 terrorist attacks in Madrid, has documented the extent to which terrorism can affect the mental health of populations [3,6] Of the specific psychiatric disorders studied, litera-ture has been mainly focused on posttraumatic stress disorder (PTSD), with several reviews documenting the
* Correspondence: jmsalguero@uma.es
1 Department of Personality, Evaluation and Psychological Treatment,
Psychology Faculty, University of Malaga, Campus de Teatinos s/n Malaga,
29071 Malaga, Spain
Full list of author information is available at the end of the article
© 2011 Salguero et al; licensee BioMed Central Ltd This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
Trang 2course and correlates of this disorder [for a review see
[1,3]] However, less is known about major depressive
disorder (MDD)
The study of MDD may facilitate a more complete
understanding of the psychopathological burden of
trauma, which may help to design more effective
popu-lation-level mental health interventions in the
after-math of terrorism [4,7-9] Terrorist attacks can
produce reactions of intense fear and horror and
gen-erate a profound sense of loss for the people involved,
both of which may underlie the development of MDD
[10,11] Moreover, a positive association between the
occurrence of stressful events and the probability of
developing a MDD has been consistently documented
in the literature [for a review, see [12,13]] Therefore,
it is plausible that MDD prevalence may increase after
disasters This, together with the high prevalence of
MDD in the general population [14,15] and the
sub-stantial personal, social, and economic consequences of
this disorder [16-18], suggests that MDD may be an
important focus in the study of the psychological
effects of terrorism
However, with few exceptions [8], most of the data on
MDD after terrorist attacks has been gathered in studies
that also present data on other psychological problems
(typically reporting MDD and PTSD jointly) and carried
out in the context of a very specific event, at a given
time and place, without comparing the results obtained
with other prevalence rates On the other hand, there is
heterogeneity in the methodology used to assess MDD,
with several studies using scales that assess the
fre-quency or intensity of certain symptoms associated with
MDD (and not diagnostic measures), that may hamper
the correct prediction of expected rates of MDD All
this limits our ability to draw generalizable inferences
about MDD after terrorist attacks and suggests that a
systematic review may make an important contribution
to the field [6]
We present a review of the empirical research focused
on the study of MDD as a consequence of terrorism in
two specific populations: direct victims (people who
experienced the event in first person either because they
were injured in the attack, or suffered material losses, or
lost relatives or close friends [19]) and indirect victims
(people in the general population) Two specific goals
were established for the review: (a) to systematically
review the results of studies that analyzed the prevalence
and course of MDD following terrorist attacks and (b)
to document the main correlates associated with this
disorder Our intention is to draw inferences that may
help future research in the field and potentially guide
the implementation of practical interventions when
ter-rorist attacks do occur
Method Selection criteria Type of event studied
Our review focused only on studies carried out after human-made, intentional, terrorist attacks, limiting our search to studies that were designed and conducted at a specific time and place and not including, therefore, investigations on the impact of other kinds of disasters (e.g., natural disasters) or chronic exposure to trauma (such as works carried out in times of war)
Type of population assessed
We focused our review on studies carried out in adult populations, including either persons in the general population or persons directly affected by a terrorist attack We excluded work that focused on specific population subgroups such as emergency personnel, children, etc
Type of assessment methodology used
Several studies in the field have adopted a dimensional approach, using scales that assess the frequency or intensity of certain symptoms associated with MDD These studies preclude a diagnosis of MDD Although some studies overcome this problem using different cut-off points to document MDD prevalence [20,21], this can lead to different conclusions depending on the cut-off point used [22] and to an overestimation of the pre-sence of this disorder in the population [23] Moreover,
it is difficult compare the prevalence of MDD reported
by investigations when a dimensional approach is used Therefore, we only took into account the assessment of MDD based on diagnostic criteria, mainly based on the DSM international classification Also, although some studies in the field use the term“incidence” rather than
“prevalence”, none of them were designed to ensure that persons were free from psychopathology before the occurrence of the terrorist attack Therefore, and follow-ing other authors [1,3], we shall use the term prevalence
in general throughout
Search strategy
Figure 1 presents the flow chart for the selection of the included studies A four-step procedure was used First, a search of the peer-reviewed literature in the PsycINFO and Medline databases was conducted (without time limit) using the following keywords: depression, terrorist, terrorism, mental health, disaster and trauma Searches were undertaken between Janu-ary 12 and 16, 2009 The initial database search identi-fied 567 potentially eligible studies for this review Second, two independent reviewers analyzed the title and abstracts of all retrieved studies and excluded those which did not meet the selection criteria The majority of studies excluded in this step were papers
Trang 3that analyzed psychological consequences different
from MDD, other kinds of disasters not categorized as
terrorist attacks or other populations that were not
either direct victims nor general population Third, full
manuscripts were obtained for all publications
included after the second step We examined the
com-plete text of the articles and once again eliminated
those which did not comply with the selection criteria
The majority of studies excluded in this step were
papers that analyzed the psychological consequences of
terrorist attacks without assessing MDD with
diagnos-tic criteria Fourth, to verify that our final sample was
comprehensive and that our search was appropriate,
we compared it with previous review papers [1,3,6]
Search Results
Our search identified 11 studies of MDD following
ter-rorist attacks: 6 were carried out with victims, 4 with
general population samples, and one with victims and
general population Of these, 9 were cross-sectional
stu-dies and 2 were cohort stustu-dies The most relevant
infor-mation of each reviewed study is summarized in
Tables 1 (studies with victims) and 2 (general
popula-tion studies) In these, informapopula-tion about the terrorist
attacks, assessment time, sample size, method and main
results (MDD prevalence) is shown
In our review, most studies examine the impact of
terrorist attacks in Madrid (March 11, 2004) and New
York (September 11, 2001) Nevertheless, one study
assesses the impact of different terrorist attacks
occurred in France (between 1982 and 1987), another
one assesses the consequences of the Oklahoma City
Bombing (1995), and yet another one compares the
consequences of the Oklahoma City Bombing with
the attack on the US embassy in Nairobi, Kenya
(1998)
The measures used to establish MDD prevalence were the Diagnostic Interview Schedule (DIS)/Disaster Supplement, based on the DSM-III-R criteria [24] (used in 2 studies); the Diagnostic Interview Schedule (DIS) based on the DSM-IV criteria, with adjustments for cultural fit [25] (used in 1 study); The Mini Inter-national Neuropsychiatric Interview (MINI), based on the DSM-IV criteria [26] (used in 2 studies); and the SCID’s major depressive disorder (MDD) interview [27], based on the DSM-IV-TR criteria (used in 5 stu-dies) In one study [28] the researches assessed MDD with 15 items created ad hoc and based on the DSM-III criteria
Results Prevalence and course of MDD after terrorist attacks Results in direct victims
One of the first studies with direct victims was carried out by Abenhaim, Dab, and Salmi [28] These authors studied the consequences of 21 terrorist attacks that occurred in France between 1982 and 1987 Data were collected between 4 months and 3 years after the attacks Results showed an overall prevalence of MDD
of 13.3%, although this depended on the degree of the effect or harm suffered by the person: 21.8% among the severely injured and 8.5% among the mildly injured or uninjured
After the Oklahoma City bombing in 1995, which caused the death of 167 people and left more than 600 wounded, several studies were carried out with persons selected from the record of victims of the Health Department of Oklahoma In the first study, using a sample of 182 victims, North et al [29] found that 22.5% of them suffered MDD between 4 and 8 months after the attacks Moreover, 56% of these reported that they had not suffered this disorder previously In another investigation, North et al [30] examined the prevalence of different mental disorders, among them MDD, in victims of two different terrorist attacks, the Oklahoma City bombing and the attack on the US embassy in Nairobi, Kenya, in 1998 The goal was to compare the mental health of populations exposed to terrorism in different continents–North America and Africa–using a similar methodology in both studies Results showed no significant differences in the preva-lence of MDD in these populations in both men and women There were no differences in the prevalence of other pathologies such as PTSD or panic disorder sug-gesting comparable consequences of terrorist events across very different contexts
In Spain, several studies analyzed the psychopathologi-cal consequences of the terrorist attacks of March 11,
2004, in Madrid In these attacks, ten bombs placed on four suburban trains caused the death of 191 people and
Potentially eligible studies identified
after the initial data base search
(n=567)
Studies excluded (n=556)
- Paper that analyze psychological consequences different from MDD
- Other kinds of disasters or chronic exposure
to trauma
- Specific populations (emergency personnel, immigrants) or children or adolescent populations
- Assessment of depression not based on diagnostic criteria
Studies included:
Studies identified from search (n=11):
- Studies with victims population (n=6)
- Studies with general population samples (n=4)
- Studies with victims and general population samples (n=1)
- Cross sectional studies (n=9)
- Cohort studies (n=2)
Abstract and title assess for
eligibility
Full-text articles assess
for eligibility
Figure 1 Flowchart of the studies included in the review.
Trang 4wounded approximately 1800 Between one and three
months after these events, Iruarrizaga, Miguel-Tobal,
Cano-Vindel and González-Ordi [31] surveyed a sample
of victims who were either in the trains or at the
sta-tions where the bombs exploded, or had lost relatives or
close friends, or whose relatives or close friends had
been wounded This study documented a prevalence of
MDD of 31.3% Similar results were found in two other
studies that assessed a sample of victims who requested
medical assistance in various Madrid hospitals on the
day of the terrorist attacks, despite differences in the
assessment instruments and the methodology between
them The prevalence of MDD was 31.5% in the first
study [32] and 28.6% in the second [33]
Results are contradictory with regard to the course of MDD In a follow-up study carried out by North [34] after the Oklahoma City bombing, only 50% of those who suffered MDD six months after the attack were still depressed one year later On the other hand, after the March 11, 2004 attacks, whereas Conejo-Galindo et al [33] found that the prevalence of MDD decreased slightly at 6 months (22.7%) they also found that the prevalence 12 months after the attacks was comparable
to what it had been 1 month after the attacks (28.6%)
Results in the general population
Terrorist attacks can have an effect on the population that is directly assaulted or even on an entire nation [20,21] Several studies have documented the
Table 1 Studies of major depression prevalence in victims of terrorist attacks
Study Assessment time Sample Method Instrument Measurement Results
Abenhaim
et al.
(1992)
Between 4 months and
3 years after the attacks
occurred in France
between 1982 and 1987
254 victims Self-report 15 items created ad hoc for this
study and based on the DSM-III criteria
Questions addressed complaints such as feeling depressed, irritability, sadness, sexual difficulties, loss of appetite, or asthenia.
Current depression (past month)
13.3%
[10% men; 17.7% women] * 21.8% among the severely injured 8.5% among the mildly injured or uninjured North et
al (1999)
6 months after the 1995
Oklahoma City bombing
182 victims Personal and
telephone interview
Diagnostic Interview Schedule (DIS)/Disaster Supplement based
on the DSM-III-R criteria[27]
22.5%
[13% men; 32% women] **
North
(2005)
6 months after the 1995
Oklahoma City bombing
Between 8 and 10
months after the attack
in Nairobi, Kenya, 1998
182 victims from the Oklahoma City bombing
227 victims from the Nairobi attack
Personal and telephone interview in the Oklahoma City study Personal interview in the Nairobi study
Diagnostic Interview Schedule (DIS) based on the
DSM-IV criteria, with adjustments for cultural fit [28]
Oklahoma: 20.9%
[11.4% men; 29.8% women] **
Nairobi: 19.4% [15.8% men; 23.6% women] * Iruarrizaga
et al.
(2004)
1 month after the M-11
terrorist attacks in
Madrid
117 direct victims
Telephone interview
SCID ’s major depressive disorder (MDD) interview [30]
Diagnostic interview based on the DSM-IV-TR criteria
Current depression
31.3%
[19.1% men; 40% women] **
Gabriel et
al (2007)
5-12 weeks after the
M-11 attacks
127 victims who requested medical assistance
Personal interview
Mini international neuropsychiatric interview (MINI), Spanish version [29]
Diagnostic interview based on the DSM-IV
Current depression (last 15 days)
31.5%†
North
(2001)
Follow-up 11 months
after the study of North
et al., 1999.
182 victims from the first assessment,
141 in the second
Diagnostic Interview Schedule
(DIS)/Disaster Supplement based
on the DSM-III-R criteria [27]
50% reduction in the
prevalence of depression between 6 months and 1 year later†
Conejo-Galindo et
al (2008)
1, 6 and 12 months
after the M-11 terrorist
attacks in Madrid
56 victims who requested medical assistance
44 second assessment
42 third assessment
Personal interview carried out by psychiatrist
Mini international neuropsychiatric interview (MINI), Spanish version [29]
Diagnostic interview based on the DSM-IV criteria
One month later:
28.6%†
6 months later: 22.7%
†
12 months later: 28.6%
†
Note: “Current depression” refers to people who suffer from major depression at the time of the interview
* Difference is not statistically significant
** Statistically significant difference
† Separate rates of depression in men and women not documented
Trang 5consequences of terrorist attacks on the population as
a whole
Galea et al [35] assessed a sample of residents of
Manhattan between 5 and 8 weeks after the September
11, 2001 World Trade Center attacks They found a
pre-valence of current MDD of 9.7% These findings were
replicated in another cross-sectional sample studied 4
months after the attacks [36]
Person et al [8] assessed the prevalence of MDD six
months after September 11 terrorist attacks in a
repre-sentative sample of the metropolitan area of New York
Data showed that the prevalence of MDD was 3.9%,
suggesting a return to baseline in MDD in the general
population 6 months after the attacks
Miguel-Tobal et al [37] carried out an epidemiological
study to document the psychological consequences of
the March 11, 2004 terrorist attacks in Madrid Using a
methodology similar to the one employed by Galea et
al [35], and adapting the instruments they used, they
assessed a representative sample of the adult population
of Madrid between 5 and 15 weeks after the attacks
The results showed a prevalence of MDD of 8% After the same event, similar results were found [32] in a sample of residents from the population of Alcalá de Henares (Madrid) The prevalence of current MDD in this case was 8.5%
Correlates of MDD after terrorist attacks
The correlates of MDD reported in the reviewed studies were classified as pretraumatic, peri-traumatic, posttrau-matic, and sociodemographic factors
Pretraumatic factors
Several of the studies discussed up to this point have shown that the probability of suffering MDD after a ter-rorist attack was increased by at least twofold among those who had experienced at least one stressful situa-tion in the 12 months prior to the terrorist attack [8,32,35,37]
Peri-traumatic factors
Variables that have an impact during or some time immediately after the attack are included in this cate-gory Among them, the emotional reaction in the
Table 2 Studies of major depression prevalence in general population
Study Assessment time Sample Method Instrument Measurement Prevalence Galea et al.
(2002)
5-8 weeks after
S-11
Representative sample of Manhattan south of 110th street
N = 998 adults
Telephone interview
SCID ’s major depressive disorder (MDD) interview [30]
Diagnostic interview based
on the DSM-IV-TR criteria
Current depression (last
30 days)
9.7% [7.3% men; 12% women]
**
Person et al.
(2006)
6 months after
S-11
Representative sample of the metropolitan area of New York
N = 2700
Telephone interview
SCID ’s major depressive disorder (MDD) interview [30]
Diagnostic interview based
on the DSM-IV-TR criteria
Depression since terrorist attacks Current depression (last
30 days)
Since terrorist attacks: 9.4% [7.9% men; 10.7% women] * Current: 3.9% [3.6% men; 4.2% women]
* Nandi et al.
(2005)
4 months after
S-11
Representative sample of New York
N = 2001
Telephone interview
SCID ’s major depressive disorder (MDD) interview [30]
Diagnostic interview based
on the DSM-IV-TR criteria
Depression since terrorist attacks
9%†
Gabriel et al.
(2007)
5-12 weeks after the
M-11 attacks
Sample of residents of Alcalá
de Henares (Madrid)
N = 485
Personal interview
Mini international neuropsychiatric interview (MINI), Spanish version [29]
Diagnostic interview based
on the DSM-IV criteria
Current depression (last
15 days)
8.5%†
Miguel-Tobal et al.
(2006)
1 month after the M-11
terrorist attacks in
Madrid
Representative sample of Madrid
N = 1589
Telephone interview
SCID ’s major depressive disorder (MDD) interview [30]
Diagnostic interview based
on the DSM-IV-TR criteria
Current depression (past month)
8%
[5.1% men; 10.6% women] **
Note: “Current depression” refers to people who suffer from major depression at the time of the interview; “Depression since terrorist attacks” refers to those who have suffered major depression at any given time since terrorist attacks.
* Difference is not statistically significant
** Statistically significant difference
† Separate rates of depression in men and women not documented
Trang 6immediate aftermath of the attack has been shown to
be a significant predictor of subsequent MDD Across
studies, the risk of developing MDD one month after
the terrorist attacks, or of still suffering from MDD six
months after the terrorist attacks, is approximately
three times higher in those with symptoms of panic
during or shortly after the attacks [8,35,37] Similar
results were shown in the people who admitted having
been afraid to die or of being injured during the attack
[37]
Posttraumatic factors
The factors or events that occurred in the weeks or
months after the terrorist attack were classified in this
category Among them, the occurrence of stressful
events or the loss of psychosocial resources after the
terrorist attacks is noteworthy Having experienced
more stressful situations after September 11, 2001,
mul-tiplied the probability of suffering from MDD by
between 1.2 and 2.4 in a representative sample of
resi-dents of New York City [8] In addition, the loss of
psy-chosocial resources has been associated with MDD in
other study [35]
Sociodemographic factors
Of all the sociodemographic variables studied, the
clear-est relation was found between gender and the risk of
MDD following the terrorist attacks, with women having
consistently higher prevalence of MDD after these
events This result has been documented in direct
vic-tims of terrorist attacks [32,33] and in the general
popu-lation [32,35,37]
Other variables commonly analyzed, such as age, race,
or ethnicity, do not show a consistent relation with
MDD in these studies For example, being Hispanic was
a significant predictor of MDD one month [35] but not
6 months [8] after the September 11, 2001 attacks or,
with respect to age, prevalence of MDD was lower in
older people after September 11, 2001 attacks [35] but
not after the March 11, 2004 terrorist attacks [37]
Nonetheless, variables such as the economical or
educa-tional level were not associated with a differential risk
for the onset of MDD
Several studies have assessed the proximity of
resi-dence to the place where the terrorist attacks occurred
and the relation of this variable with subsequent MDD
In contrast with the findings in the assessment of PTSD
[3], the proximity of one’s residence has not been
con-sistently shown to be a predictor variable of MDD, at
least in the works with general population [37]
Results are inconsistent with respect to social support
Whereas in some studies the perception of social
sup-port in the months prior to the terrorist attack was
shown to be a negative predictor of MDD [35,37], in
other works no significant association between these
variables was found [8,32]
Overview of the excluded studies
Excluded studies that assess the prevalence of other psy-chological problems after terrorist attacks have generally been focused on PTSD The research literature suggests that the burden of PTSD in persons exposed to disasters
is significant Specifically, the prevalence of PTSD among direct victims ranges between 30% and 40%, while the range in the general population is between 5% and 10% [see 3 for a review] Furthermore, a common result is that the prevalence of PSTD in the aftermath of
a natural disaster is often lower than the rates documen-ted after human-made disasters (such as terrorist attacks) [1,3,6]
Other studies not included in our review examined the prevalence of MDD after natural disasters or chronic exposure to trauma Some of the natural disasters evalu-ated have been the 1999 Turkey earthquakes [38], the
2004 Asian Tsunami [39], the 2004 hurricane in Florida [40] or the 2005 hurricane Katrina [41] Natural disas-ters affect broad geographic areas, leading investigators
to study populations that often include both direct and indirect victims [3] Consequently, reports of MDD pre-valence rates after natural disasters vary widely For instance, a study on the Turkey earthquakes showed a higher prevalence of MDD closer to the epicentre (16%) compared to 100 km away (8%) [38] Another study on the Asian tsunami found a higher prevalence of MDD
in displaced people (30%) than in two other samples of non-displaced people (21% and 10%, respectively) [39] Focused on chronic exposure to trauma, different stu-dies have examined the significant impact of terrorism
in the Israeli population since the beginning of the Al Aqsa intifada in September 2000 In a study conducted
in April-May 2002, Bleich et al [42] showed that over half of a national representative sample of Israel reported feeling depressed In another population-based study carried out between January 2002 and December
2005 [43], 15.4% of participants reported a MDD, with rates of MDD being 2.4 times higher among Arab Israe-lis than among Jews This difference between Arabs and Jews has been shown in other studies, and is consistent with both MDD as well as other psychological problems [44,45], suggesting that the mental health impact of ter-rorism differs among diverse groups living in Israel Along the same line, different authors have documented the psychological impact of impending forced settler dis-engagement in Gaza Hall et al [46] assessed a sample
of Israeli settlers who, after having been exposed to ongoing terrorism, were forced to leave their homes The prevalence of MDD was 16.8%, 5 times greater than that of settlers living in the occupied territories before the Gaza disengagement Other papers have assessed the predictors of depressive symptoms in population-based cohort studies [11,47]
Trang 7Together with victims and general population, specific
population sub-groups (e.g., emergency personnel or
children and adolescents) have also been evaluated In
contrast to the findings in the assessment of PTSD,
where the prevalence of PTSD among rescue workers is
higher than in the general population [4], prevalence of
MDD in rescue workers seems to be lower than in
vic-tims or in general populations, as different studies
car-ried out after March-11 terrorist attacks have clearly
shown [48] On the other hand, the impact of terrorism
in children and adolescents reveals that a substantial
proportion of youth reports a wide array of clinical
needs and functional impairments months after an
attack [see 49 for a review] The role of protective
fac-tors for depression in adolescents has also received
attention in the literature For example, two prospective
studies documenting changes in depressive symptoms
(as measured by CES-D) in Israeli adolescents exposed
to missile attacks [50] and suicide bombings [51]
showed that social support (mainly friendly social
sup-port) buffers the effect of terrorism-related perceived
stress in predicting changes in depression
Discussion
The reviewed literature suggests that terrorist attacks
are a risk factor for the development of MDD, mainly in
the first months after its occurrence, and in certain
at-risk populations The at-risk of MDD ranges between 20
and 30% in direct victims of terrorist attacks and
between 4 and 10% in the general population in the first
few months after terrorist attacks These prevalence
rates are 2-3 times higher than might be expected
according to general population surveys [14,15] These
results are consistent across studies that have used
sepa-rate methodologies and assessment instruments after
different terrorist attacks occurring in various cities [as
in the case of the studies 35 and 37, or the study 30]
This suggests that the consequences of terrorist attacks
may be universal and, in some respects at least,
inde-pendent of context
It is not easy to perform longitudinal investigations
after the occurrence of terrorist attacks and the scarcity
of studies in this area limits clear inference Thus,
whereas in some studies the prevalence of MDD in
vic-tims has decreased over time [34], in other studies, it
has remained relatively stable [33]
There are several risk factors that have consistently
been shown to be associated with the risk of suffering
from MDD after a terrorist attack These include having
undergone stressful situations before or after the attack,
having suffered a panic attack during the attack, being
female, and having borne a greater loss of psychosocial
resources Although high perceived social support has
been shown to be a protector factor for the onset of
other psychological problems in several studies [1], this result is inconsistent in relation to MDD This inconsis-tency in the published studies may suggest the existence
of moderating and/or mediating variables in the relation between social support and MDD after terrorist attacks Previous literature has noted that severe levels of impairment are most likely to occur in people exposed
to terrorism than to any other types of disaster, such as natural disasters [1,6] Consistent with these observa-tions, the prevalence of MDD reported in our review appears to be higher than that reported after natural disasters [38-41] Terrorism has been distinguished from natural disasters by its capacity to produce greater sense
of fear, loss of confidence in institutions, unpredictabil-ity and pervasive experience of loss of safety [4] These characteristics may be associated with the increased risk
of psychiatric morbidity after terrorism However, the different rates of MDD after natural disasters and ter-rorist attacks may be due to differences in the samples assessed among studies After natural disasters, it is dif-ficult to classify persons as either direct or indirect vic-tims [3] and, consequently, the study sample may include persons who were more or less directly exposed
to the disaster [6]
Together with MDD, some of the reviewed studies assessed the prevalence of PTSD and some examined the comorbidity between MDD and PTSD Given the evidence indicating the high rates of comorbidity between MDD and PTSD following trauma [52,53], it is likely that MDD seldom happens in isolation after ter-rorist attacks In this respect, one study examined in this review [37] reported high rates of comorbidity in general population, with around 50% of individuals with MDD having comorbid PTSD one month after S-11, and around 30% with MDD having comorbid PTSD one month after M-11 Similar results were reported in direct victims exposed to the Oklahoma City Bombing (55% of subjects with PTSD were also diagnosed as hav-ing MDD) [29] The mechanisms linkhav-ing PTSD and MDD remain unclear, with alternative explanations including PTSD and MDD as a single general traumatic stress construct [54], comorbid MDD developing as a secondary reaction [55] or MDD and PTSD as relatively independent posttraumatic disorders [56] Reviewed stu-dies show that MDD is not always concurrent with PTSD and suggest that, consistent with previous studies carried out after other traumatic events [52,53], both disorders can be considered related but different post-traumatic reactions In this regard, Rubacka et al [57], examining the specific association of PTSD cluster symptoms (re-experiencing, avoidance, and hyperarou-sal) and MDD in a sample of mothers directly exposed
to the WTC attacks, showed that only higher arousal symptom scores were significantly correlated with
Trang 8persistent MDD Furthermore, if we compare the rates
of MDD and PTSD found in some reviewed reports, we
can reach some interesting conclusions Whereas in
direct victims the probability of developing PTSD after
terrorism is higher than that of MDD (with percentages
of PTSD usually over 30%), this tendency is reversed in
the general population For example, the prevalence of
PTSD and MDD in the general population was 7.5%
and 9%, respectively, after S-11 [35,36], and 2.3% and
8%, respectively, after M-11 [37] These results support
those found in previous research [53,56], suggesting that
the pathways to MDD and PTSD may by somewhat
dis-tinct; whereas the intensity of the attack and the degree
of exposure may be more closely involved in the
devel-opment of PTSD, bereavement and psychosocial loss
may underlie MDD after a terrorist attack [10,37]
The aim of the current work was to review the
evi-dence regarding MDD following terrorism There are
some limitations to the literature in the field and to our
review that need to be taken into account when
inter-preting the results herewith presented
Limitations of the literature in the field
First, although we only included studies that assessed
MDD based on diagnostic criteria, most of them used
instruments that did not include an assessment of either
manic or psychotic symptoms, therefore we could not
classify the disorder beyond probable MDD [8]
Although the prevalence of bipolar affective disorder is
not much higher than 1% [14] it could be inflating the
MDD percentages Future investigations should take this
into account in order to help improve our
understand-ing of the psychopathological processes involved
Sec-ond, as we mentioned in the selection criteria section,
the reviewed studies were not designed to ensure that
persons were free from psychopathology before the
occurrence of the terrorist attacks, which means that
prevalence, instead of incidence, was assessed
More-over, none of them included a control group that would
enable the comparison between exposed and
non-exposed populations We overcame this challenge by
comparing the prevalence of MDD following terrorism
with the prevalence reported in other general population
surveys However, it is important to be cautious when
interpreting this comparison because the majority of
these epidemiologic studies are referred to a whole
nation’s population (e.g Spain or United States) [15,58]
and not to the city where terrorist attacks occurred (e.g
Madrid or New York), hence there could be differences
between the two Future studies should attempt to
ana-lyze the incidence of MDD by establishing baseline
psy-chopathological assessments that may be used as
population cohorts to document MDD incidence in the
event of terrorism exposure Third, there are several
challenges facing longitudinal studies that aim to docu-ment the course of MDD Several studies suffer from attrition, that is, the reduction in the number of people who participated in the follow-up studies This may have biased the prevalence estimates of MDD, especially
in the case of small samples [33] Fourth, we have to be careful when extracting conclusions with respect to some correlates of MDD, mainly the pre-traumatic fac-tors In the reviewed studies, the assessments documen-ted always took place after the terrorist attack in question It is possible that pre-event reports are biased
in the sense that depressed persons may selectively recall stressful situations that occurred before the attack
to a greater extent than non-depressed persons
Limitations of the review
In relation to the characteristics of our review, we only considered studies that had assessed samples of direct
or indirect adult victims Even though we did not include studies that assessed children or adolescents, further work with this age group is clearly warranted
We also limited our search to studies that analyzed the consequences of terrorist attacks and not other kinds of disasters; knowing and comparing the prevalence and course of MDD after natural, technological, or other dis-asters linked to interpersonal violence (such chronic exposure to trauma) could help us understand the onset
of mental disorders after mass traumatic events Finally,
we have focused our review on the examination of MDD using diagnostic criteria This enables us to com-pare prevalence rates of MDD with previous epidemio-logical surveys and between studies carried out after different terrorist attacks However, MDD is not the sole disorder within the unipolar spectrum and extant research after terrorism has also highlighted the high prevalence and impairment associated with other forms
of depression, such as mild or minor depression Includ-ing these other forms of depression, together with the risk factors associated with it, could be of research and public health interest
Implications for future research in this field
Our review highlights some key areas that are important for future research and may serve to guide intervention First, the course of MDD after terrorist attacks remains unclear That is why greater efforts are needed to eluci-date the course of MDD after terrorist attacks Second, there is very limited literature about psychological con-structs that may be associated with MDD after terrorist attacks [3,9] It would be interesting, in this context, to analyze the role played by other variables that have been shown to be related to MDD, such as attributional style [59], self-esteem [60] or response styles to depression [61], and to examine the way in which certain
Trang 9psychological variables interact with other
sociodemo-graphic variables to predict the onset of MDD For
example, it is possible to analyze which psychological
factors mediate the relationship between MDD and
gen-der This line of research will be useful in helping to
identify the persons with higher probability of
develop-ing MDD followdevelop-ing a terrorist attack and to improve
the efficacy of the interventions from which they will
benefit Third, more research is needed on the role of
MDD in psychiatric comorbidity after terrorist attacks
Although some reviewed studies have reported high
rates of comorbidity between MDD and PTSD, more
works are needed to have a better understanding of this
relationship For example, an interesting objective would
be to examine the form in which both pathologies vary
over the time after terrorism In this line, some authors
have recently documented the important role that
depressive symptoms plays in the development and
per-sistence of stress post-traumatic symptoms after
differ-ent traumatic evdiffer-ents [62] Fourth, some of the studies in
this revision included victims who had been bereaved
[33,37] Although not reported in these papers,
differ-ences in the prevalence of MDD may exist between
vic-tims who have been directly injured by a terrorist attack
and those who have been bereaved Moreover, bereaved
people could develop other psychological problems,
such as complicated grief syndrome A number of
stu-dies support the differentiation between complicated
grief and MDD [63,64], and some authors have shown
that it is a usual reaction in bereaved people after
ter-rorism [65] A clear definition of victims in future works
could provide us with a better understanding of the
psy-chological consequences in people directly and strongly
exposed to terrorism
Conclusions
The studies reviewed here, together with future research
efforts in this field, should help to inform planned
pub-lic mental health response that aims to mitigate the
con-sequences of terrorist attacks by estimating the possible
number of persons with MDD after such attacks, the
potential course of the psychopathological burden, and
the detection of populations at risk of developing these
problems
List of abbreviations used
MDD: Major Depressive Disorder; DSM: Diagnostic and Statistical Manual of
Mental Disorders; M-11: March 11, 2004 terrorist attacks in Madrid; S-11:
September 11, 2001 terrorist attacks in New York; PTSD: Posttraumatic Stress
Disorder.
Author details
1 Department of Personality, Evaluation and Psychological Treatment,
Psychology Faculty, University of Malaga, Campus de Teatinos s/n Malaga,
29071 Malaga, Spain 2 Department of Basic Psychology, University of Malaga,
3
Madrid, Madrid, Spain 4 Department of Epidemiology, Columbia University, New York City, New York, USA.
Authors ’ contributions JMSN, PFB, II and ACV were responsible for the conception and design of the study JMSN and PFB performed the databases search and the initial revision of abstracts JMSN, PFB and II reviewed the chosen studies in depth JMSN was responsible for writing the drafts of this paper ACV and SG were responsible for revising the paper critically for important intellectual content All authors read and approved the final manuscript.
Competing interests The authors declare that they have no competing interests.
Received: 14 March 2011 Accepted: 1 June 2011 Published: 1 June 2011 References
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